Abstract
Background The magnitudes of the first (WI1) and the second wave-intensity peak (WI2) during the ejection period can be used as indices of left ventricular (LV) contractility and relaxation, respectively. However, use of WI to characterize LV dp/dt and the end-diastolic volume (Ved) relationship may be more problematic, as WI may be affected by changes in preload. Methods and Results The LV pressure-volume data sets, consisting of 23 recordings obtained by the conductance method from 12 heart disease patients, were studied. End-systolic elastance (Ees) and volume-axis-intercept (V0) were calculated with varying preload. Time constant of LV relaxation (τ), Ved, and WI were calculated from steady-state averaged data. The Ees showed a weak correlation with WI1 (r=0.46, p<0.05) but a better correlation with preload-adjusted WI1 [WI1/V ed; r=0.86, WI1/Ved2; r=0.92, WI1/(Ved - V0)2; r=0.89, all p<0.01]. Similarly, τ did not correlate with WI2 but did correlate with preload-adjusted WI2 [WI 2/Ved; r=-0.73, WI2/Ved 2; r=-0.63, WI2/(Ved - V0) 2; r=-0.78, all p<0.01]. Conclusions These data demonstrate the importance of preload-adjustment when using the WI index for simultaneous assessment of LV contractility and relaxation. (Circ J 2005; 69: 683 - 687)
